The washing depends on the material of faraday fabric. The majority of faraday fabric is metallic fabric which feels tough and coarse. For example, the copper nickle fabric is not suitable for machine washing. It's better to clean it with a wet rag.
For other soft faraday fabrics like silver faraday fabric, maching washing is acceptable. This kind of fabric is good for making clothing like t-shirts and hoodies. But excessive washing will also reduce the emp defense effectiveness of the fabric.